In library science, special collections (often abbreviated to Spec. Coll. or S.C.) is the name applied to a specific repository or department, usually within a library, which stores materials of a "special" nature, including rare books, archives, and collected manuscripts. Works kept in special collections (as opposed to the library's general collection) are typically stored there because they are unusually valuable, rare (possibly unique), or fragile, or because they should not, for some particular reason, be allowed to commingle with the library's other works.

The primary function of a special collections department is to keep holdings safe and secure while remaining accessible. Special collections are usually closed stacks and the items usually noncirculating; the items are mostly accessible only to properly qualified interested researchers. These researchers- who must usually present IDs, letters of reference, and credentials to gain full access- are generally graduate students and faculty. Special collections materials are typically non-circulating (meaning that they cannot ordinarily be loaned out) and ideally should be stored in areas where the temperature, humidity, illumination, and other environmental conditions are carefully monitored, and adequate security provided to protect the materials from unauthorized access, theft, and vandalism. Special reading rooms are often provided to minimize the risk to holdings while being consulted by library users, and conditions on such use (such as the use of gloves, or prohibitions on flash photography or the use of writing implements with ink) are likely to be imposed in order to protect the works.